On Monday, the United States Postal Service began to issue their new Parks stamps -- called forever stamps because their rates never change -- to honor the civil-rights figure, who died in 2005. The stamp shows a portrait of Parks painted by Thomas Blackshear II. Monday would have been her 100th birthday.

In 1955, in Montgomery, Ala., Parks -- then 42 years old -- refused to give up her seat on a city bus so that a white man could sit down. This broke the law; buses at that time were segregated. She was arrested.

Some consider this view of Parks oversimplified, a view presented in a new book by Jeanne Theoharis, released last week, called "The Rebellious Life of Mrs. Rosa Parks."

"The trend among scholars in recent years has been to de-center Parks in the story of the early civil rights movement, focusing on the role of other activists in Montgomery; on other people like Claudette Colvin who had also refused to give up their seats; and on places other than Montgomery that helped give rise to the movement," Theoharis writes. "While this has provided a much more substantive account of the boycott and the roots of the civil rights movement, Rosa Parks continues to be hidden in plain sight."

According to Theoharis, Parks' personal hero was Malcolm X -- a militant figure within the civil-rights firmament who stood in contrast with King -- and she had long been politically active before the 1955 bus arrest. Prior that incident, she'd refused to petition for better treatment on the buses, saying, "I had decided I would not go anywhere with a piece of paper in my hand asking white folks for any favors."

Parks said she hadn't planned the incident, but she also dismissed the widespread notion that it happened because her feet were tired.

"I didn't tell anyone my feet were hurting," she recalled later. "It was just popular, I suppose because they wanted to give some excuse other than the fact that I didn't want to be pushed around."

She continued her activism in later life, opposing Vietnam and apartheid in South Africa, and organizing decades' worth of protests over inequality in Detroit, her home in later years.

After Parks' death at 92, she became the first woman to lie in honor in the U.S. Capitol rotunda.